Shape memory polymers (SMPs) are polymers which regain their original shape when heated above their glass transition temperature (Tg). Articles are formed from shape memory polymers by first heating them above the glass transition temperature and then shaping the polymer, then subsequently fixing the shape by cooling to below the glass transition temperature. During subsequent deployment, the shaped article is heated above the glass transition temperature to allow recovery of the first molded shape.
A variety of shape memory polymers (SMPs) have been used in numerous areas. In particular, SMPs have been used in downhole environments (e.g., oil and natural gas production) as sealing members and filters. However, deployment of the SMP has involved thermal activation. In thermal activation, the temperature of the SMP is increased above the glass transition temperature (Tg) of the SMP to recover its original shape. As a thermal activation medium, heated downhole fluids are used to increase the temperature of the SMP to greater than its Tg.
U.S. Patent Application Publication No. 2011/0252781 to Johnson, et al. and assigned to Baker Hughes Incorporated discloses that the actuation and control of the deployment of a polymeric memory-shape material (SMP) on a wellbore device on a downhole tool may be accomplished by treating a compacted or compressed polymeric memory-shape material with a deployment fluid to lower its Tg and/or decrease its rigidity, thereby softening the polymeric shape-memory material at a given temperature and triggering its expansion or recovery at a lower temperature. Alternatively, the deployment of the compacted or compressed polymeric memory-shape material may be prevented or inhibited by shielding the material with an environment of a fluid that does not substantially lower its Tg, decrease its rigidity or both, and then subsequently contacting the material with a deployment fluid. Chemicals used as deployment fluids or activation fluids should exhibit high flash points to be safely utilized in the field.
Alternatives to thermal activation of SMP articles downhole would be well-received in the art. It would be desirable to raise the flash points of deployment fluids or activation fluids to make them safer to handle.